Method for improving the fire resistance of nylon and polyester fabrics

ABSTRACT

The resistance to burning and flame proprogation of synthetic textile fabrics, such as nylon and polyester is improved by treatment with an aqueous solution of formaldehyde and ammonium thiocyanate and drying.

Unite States ate t 1191 1111 3,785,858 Chapin 1 Jan. 15, 1974 [54] METHOD FOR IMPROVING THE FIRE 2,922,726 1 1960 Morreti et a1 117/137 RESISTANCE 0F NYLON AND POLYESTER 3,600,219 8/1971 Reuter et a1 l l7/l38.8 F FABRICS 3,669,725 6/1972 Nachbur et al. 117/136 3,692,559 9/1972 Powell 117/138.8 F

[75] Inventor: Jay C. Chapin, Marblehead, Mass.

[73] Assignee: Ventron Corporation, Beverly,

Mass.

[22] Filed: June 19, 1972 [21] Appl. No.: 264,342

[52] US. Cl 117/136, 117/137,117/138.8 N, 117/138.8 F, 252/8.1 [51] Int. Cl C09d 5/18 [58] Field of Search 117/136, 138.8 N, 117/138.8 F, 139.5 CQ, DIG. 3, 137; 252/8.1; 106/15 PF [56] References Cited UNITED STATES PATENTS 2,436,181 2/1948 Rosser 117/136 OTHER PUBLICATIONS Schmerda, J. Soc. Chem. Ind., 36, 942, Aug. 31, 1917.

Primary Examiner-William D. Martin Assistant ExaminerTheodore G. Davis Attorney-4. Harold Boss [57] ABSTRACT The resistance to burning and flame proprogation of synthetic textile fabrics, such as nylon and polyester is improved by treatment with an aqueous solution of formaldehyde and ammonium thiocyanate and drying.

2 Claims, No Drawings METHOD FOR IMPROVING THE FIRE RESISTANCE OF NYLON AND POLYESTER FABRICS The invention relates to a method for treating synthetic textile fabrics, such as nylon and polyester, to imprive their resistance to burning and flame proprogation.

In accordance with the method of the invention the synthetic fabric is saturated with an aqueous solution containing from about 6 to 24 percent by weight of formaldehyde and about 20 to 28 percent by weight of ammonium thiocyanate both by weight based on the dry weight of the fabric. Excess solution is removed and the treated fabric dried at a temperature between room temperature and 275F. to cause the fonnaldehyde and ammonium thiocyanate to react to form a polymer. Unreacted material is removed by rinsing with water. The reaction product is resistant to removal by drying cleaning and laundering procedures.

The reaction of ammonium thiocyanate with formaldehyde has been previously described by Schmerda, J. Soc. Chem. lnd., 36,942. When reacted wih equimolar quantities of formaldehyde and ammonium thiocyanate in concentrated aqueous solution yellow amorphous compounds are obtained which have no definite melting points. With the use of different ratios of formaldehyde and ammonium thiocyanate different types of resins have been obtained.

Whan an aqueous solution of formaldehyde and ammonium thiocyanate is prepared and permitted to stand the pH of the solution gradually decreases as shown in Table I.

With a ratio of BM CHgOilM NH SCN the change in pH of the solution was similar. With a ratio of 2M CH OIIM NH SCN a drop of pH was also noted. The pH drop of the solution could be retarded by keeping the solution below C. After an hour with all three solutions at a temperature of about 27C a precipitation of solid polymer had commenced. At the end of 24 hours the weight of solid polymer from the 3 solutions was determined. See Table ll.

Table II Yield From Reaction of CH,O and NH.SCN

These polymers are insoluble in chlorinated hydrocarbons such as are used for dry cleaning and also are not soluble in caustic solution.

Example 1 Because of the rapidity with which these polymers form treatments of fabrics must be made shortly after solution or provision made for keeping the treating solution at a temperature of l0C or lower. Within 5 minutes of making up a 1:] molar solution containing 76 grams of NH SCN, 86 grams of 37% CH O and 100 grams of water a 6.5 oz/yd polyester drapery fabric of the polyester/Dacron type was padded through the treating solution and excess solution was squeezed out until the wet pickup, based on the original dry weight of the fabric was percent. After treatment of the fabric was dried 5 minutes at 250F. in a hot air circulating oven. After drying the fabric was weighed and then rinsed of unreacted material and weighed again. The rinsing step removed about half of the dry add-on deposited on the fabric. The rinsed fabric after drying when tested in accordance with Flame Retardant Method 34-1969 AATCC was found to be immediately self extinguishing after removal of the ignition source. A glass thread was not stitched into the fabric as the method suggests for thermo plastic fabrics. Also little smoke generation was noted and the ignited fabric did not drip durig a 12 sec. ignition exposure. This fabric was also self extinguishing after one Tide washing in an automatic home washing machine.

EXAMPLE II A treating solution in a 2 to I molar ratio was made up containing 166 grams of 37% CH O solution and 76 grams of NH SCN and 17 grams of water. Polyester fabric was treated from this solution in a manner similar to that of Example l. This fabric was also immediately self extinguishing after removal of the 12 sec. ignition flame. The handle of this fabric was slightly stiff after rinsing.

EXAMPLE lll The results of these 3 examples are summarized in Table lll.

Table III Reaction of various molar ratios of CH O and NH SCN on polyester After flamming Example Ratio after drying after rinse AATCC 34-1969 l 1M CH O lM NH SCN 19.3 9.5

ll 2M CH,O

lM NH SCN 26.2 22.4 -0- l l 1 l/2M CH O 1M NH SCN 18.3 5.6

o.w.f. original weight of fabric EXAMPLE IV A treating solution was made up containing 80 grams NH SCN, 128 grams of 37% CH O and 196 grams of water. This provided a solution containing about 12 percent by weight of formaldehyde and about 20 percent by weight of NH SCN. An 8.0 oz/yd nylon upholstery fabric treated from this solution had a wet pickup based on the original weight of the fabric of 95%. The upholstery fabric was dried in a hot air circulating oven for 5 mins. at 275F. This fabric was immediately self extinguishing after 12 sec. ignition in accordance with Method 34-4969 AATCC. (A glass thread was not stiched into the fabric as the method suggests for thermoplastic fabrics). This fabric also did not drip during ignition and there was little smoke observed.

I claim:

1. The method for improving the resistance to burning and flame proprogation of synthetic textile material selected from the group consisting of nylon and polyester, which comprises saturating the textile material with an aqueous solution containing from about 6 to 24 percent by weight of formaldehyde and about 20 to 28 percent by weight of ammonium thiocyanate based upon the dry weight of the textile material, drying the treated textile material at a temperature between room temperature and about 275F. thereby causing the formaldehyde and Nl-LSCN to react to form a polymer, and removing unreacted material from the treated textile material by rinsing with water.

2. The method as claimed by claim 1 wherein the amount of formaldehyde in the aqueous treating solution is about 20 percent by weight of ammonium thiocyanate based upon the dry weight of the textile material and about 12 percent by weight of formaldehyde based on the dry weight of the textile material. 

2. The method as claimed by claim 1 wherein the amount of formaldehyde in the aqueous treating solution is about 20 percent by weight of ammonium thiocyanate based upon the dry weight of the textile material and about 12 percent by weight of formaldehyde based on the dry weight of the textile material. 